Mobility aids that are currently available in developing countries do not fully meet users’ needs. People require a device that is maneuverable within the home and that can travel long distances on rough roads. To address this problem, we have designed the Leveraged Freedom Chair (LFC), a wheelchair-based mobility aid capable of navigating virtually any terrain by optimally utilizing upper body power for propulsion through a variable-speed lever drivetrain. The lever system achieves a 4:1 change in mechanical advantage, equating to leverage that ranges from 0.42X to 1.65X a standard wheelchair hand rim. In comparative trials, the LFC demonstrated capabilities that far exceed those of any mobility aid currently available in the developing world; it was able to cruise on smooth surfaces at 2m/s (5mph), climb muddy, grassy hills with a 1:3 slope, and navigate terrain with a coefficient of rolling resistance as high as 0.48. This operational flexibility should make the LFC usable on any terrain, from rural walking paths to tight indoor confines, and greatly increase the mobility of people with disabilities in developing countries. The LFC may also be attractive to wheelchair users in developed countries, as its performance breadth exceeds that of currently available products.

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